In the petroleum industry, injection and production tubings are disposed within a borehole for injecting steam into the borehole and for producing oil from subsurface bearing formations to the surface, respectively. This tubing is comprised of elongate sections threaded together to form the injection and production strings.
Downhole tubing must operate in a harsh thermal, mechanical and chemical environment. The tubing and any coating, if applied, on the tubing can be exposed to aromatic organic compounds and steam at very high temperatures (200-260° C.) and possibly high pressures. Where the tubing is used in oil extraction from tarsands, there can also be considerable abrasion of the tubing and its external coating, if applied. Also, where the downhole tubing is assembled by screwing together threaded pipe sections, substantial forces may be exerted on the pipe and any exterior coating on the pipe during assembly of the pipe string. All these factors can limit the type of coating that can be applied to the tubing.
During production operations, pipe clogging solids can become an issue if hot hydrocarbons are allowed to cool as they flow out of hydrocarbon reservoirs. Specifically, as temperature decreases, the flow through pipelines can be impeded by high viscosity and wax formation in liquid products such as tar/bitumen, and by hydrate formation in products such as natural gas. This can also result in significantly reduced internal flow diameters of production piping and well productivity.
These problems can be reduced by using vacuum insulated pipelines, but such insulated pipelines can be expensive.
Accordingly, there is a need in the art to provide an effective thermal insulation material for the external coating of pipes used for downhole tubing. Further, there is a need in the art for a thermal insulation coating having sufficient strength and compressibility to withstand the rough handling of pipe normally associated with the production process of hydrocarbons. Moreover, there is a need in the art for a process for application of such an external coating on pipes used in downhole tubing.